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An amplifier has an operating spot noise figure of 10 dB when driven by a source of effective noise temperature 225 K.
Que: If a matched attenuator with a loss of 3.2 dB isplaced between the source and the amplifier's input,what is the operating spot noise figure of the attenuator's amplifier cascade if the attenuator's physicaltemperature is 290 K ?
- a)9 dB
- b)10.4 dB
- c)11.3 dB
- d)13.3 dB
Correct answer is option 'D'. Can you explain this answer?
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An amplifier has an operating spot noise figure of 10 dB when driven b...
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An amplifier has an operating spot noise figure of 10 dB when driven b...
Given:
- Operating spot noise figure of the amplifier = 10 dB
- Effective noise temperature of the source = 225 K
- Loss of the matched attenuator = 3.2 dB
- Physical temperature of the attenuator = 290 K
To find: Operating spot noise figure of the attenuator-amplifier cascade
Formula:
- Noise figure (NF) = (SNR_in / SNR_out - 1) * 10, where SNR is signal-to-noise ratio
- SNR_in = (P_in_signal + P_in_noise) / P_in_noise
- SNR_out = (P_out_signal + P_out_noise) / P_out_noise
- P_in_noise = k * T * B, where k is Boltzmann's constant, T is temperature in Kelvin, and B is bandwidth
- P_out_noise = NF * k * T * B
Calculation:
- Since the attenuator is matched, there is no reflection loss and the effective noise temperature seen by the amplifier is the same as the physical temperature of the attenuator, i.e., Teff = Ta = 290 K
- Noise temperature seen by the amplifier = (Teff - Loss) / Loss, where Loss is the loss in dB
- Noise temperature seen by the amplifier = (290 - 3.2) / 3.2 = 88.75 K
- P_in_noise = k * Teff * B = 1.38e-23 * 290 * B = 4.002e-21 * B
- P_out_noise = NF * k * Teff * B = NF * 1.38e-23 * 88.75 * B = 1.224e-23 * NF * B
- SNR_in = (P_in_signal + P_in_noise) / P_in_noise = (P_in_signal / P_in_noise + 1)
- SNR_out = (P_out_signal + P_out_noise) / P_out_noise = (P_out_signal / P_out_noise + 1)
- NF = (SNR_in / SNR_out - 1) * 10 = (P_in_signal / P_in_noise) / (P_out_signal / P_out_noise) * 10 - 10
- From Friis' formula, gain of the amplifier = 10^(GdB / 10) = 10^(NF / 10) = G
- P_out_signal = G * P_in_signal
- P_out_noise = G * P_in_noise
- SNR_in = (P_in_signal / P_in_noise + 1) = (G * P_out_signal / P_in_noise + 1)
- SNR_out = (P_out_signal / P_out_noise + 1) = (G * P_in_signal / P_out_noise + 1)
- Substituting the values, we get:
- NF = (4.002e-21 * B / P_in_signal) / (1.224e-23 * NF * B / G / P_in_signal) * 10 - 10
- G = 10^(NF / 10)
- P_out_signal = G * P_in_signal
- P_out_noise = G * P_in_noise
- SNR_in = (G * P_out_signal / P_in_noise +
- Operating spot noise figure of the amplifier = 10 dB
- Effective noise temperature of the source = 225 K
- Loss of the matched attenuator = 3.2 dB
- Physical temperature of the attenuator = 290 K
To find: Operating spot noise figure of the attenuator-amplifier cascade
Formula:
- Noise figure (NF) = (SNR_in / SNR_out - 1) * 10, where SNR is signal-to-noise ratio
- SNR_in = (P_in_signal + P_in_noise) / P_in_noise
- SNR_out = (P_out_signal + P_out_noise) / P_out_noise
- P_in_noise = k * T * B, where k is Boltzmann's constant, T is temperature in Kelvin, and B is bandwidth
- P_out_noise = NF * k * T * B
Calculation:
- Since the attenuator is matched, there is no reflection loss and the effective noise temperature seen by the amplifier is the same as the physical temperature of the attenuator, i.e., Teff = Ta = 290 K
- Noise temperature seen by the amplifier = (Teff - Loss) / Loss, where Loss is the loss in dB
- Noise temperature seen by the amplifier = (290 - 3.2) / 3.2 = 88.75 K
- P_in_noise = k * Teff * B = 1.38e-23 * 290 * B = 4.002e-21 * B
- P_out_noise = NF * k * Teff * B = NF * 1.38e-23 * 88.75 * B = 1.224e-23 * NF * B
- SNR_in = (P_in_signal + P_in_noise) / P_in_noise = (P_in_signal / P_in_noise + 1)
- SNR_out = (P_out_signal + P_out_noise) / P_out_noise = (P_out_signal / P_out_noise + 1)
- NF = (SNR_in / SNR_out - 1) * 10 = (P_in_signal / P_in_noise) / (P_out_signal / P_out_noise) * 10 - 10
- From Friis' formula, gain of the amplifier = 10^(GdB / 10) = 10^(NF / 10) = G
- P_out_signal = G * P_in_signal
- P_out_noise = G * P_in_noise
- SNR_in = (P_in_signal / P_in_noise + 1) = (G * P_out_signal / P_in_noise + 1)
- SNR_out = (P_out_signal / P_out_noise + 1) = (G * P_in_signal / P_out_noise + 1)
- Substituting the values, we get:
- NF = (4.002e-21 * B / P_in_signal) / (1.224e-23 * NF * B / G / P_in_signal) * 10 - 10
- G = 10^(NF / 10)
- P_out_signal = G * P_in_signal
- P_out_noise = G * P_in_noise
- SNR_in = (G * P_out_signal / P_in_noise +
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An amplifier has an operating spot noise figure of 10 dB when driven by a source of effective noise temperature 225 K.Que: If a matched attenuator with a loss of 3.2 dB isplaced between the source and the amplifier's input,what is the operating spot noise figure of the attenuator's amplifier cascade if the attenuator's physicaltemperature is 290 K ?a)9 dBb)10.4 dBc)11.3 dBd)13.3 dBCorrect answer is option 'D'. Can you explain this answer?
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An amplifier has an operating spot noise figure of 10 dB when driven by a source of effective noise temperature 225 K.Que: If a matched attenuator with a loss of 3.2 dB isplaced between the source and the amplifier's input,what is the operating spot noise figure of the attenuator's amplifier cascade if the attenuator's physicaltemperature is 290 K ?a)9 dBb)10.4 dBc)11.3 dBd)13.3 dBCorrect answer is option 'D'. Can you explain this answer? for Electronics and Communication Engineering (ECE) 2024 is part of Electronics and Communication Engineering (ECE) preparation. The Question and answers have been prepared according to the Electronics and Communication Engineering (ECE) exam syllabus. Information about An amplifier has an operating spot noise figure of 10 dB when driven by a source of effective noise temperature 225 K.Que: If a matched attenuator with a loss of 3.2 dB isplaced between the source and the amplifier's input,what is the operating spot noise figure of the attenuator's amplifier cascade if the attenuator's physicaltemperature is 290 K ?a)9 dBb)10.4 dBc)11.3 dBd)13.3 dBCorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for Electronics and Communication Engineering (ECE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for An amplifier has an operating spot noise figure of 10 dB when driven by a source of effective noise temperature 225 K.Que: If a matched attenuator with a loss of 3.2 dB isplaced between the source and the amplifier's input,what is the operating spot noise figure of the attenuator's amplifier cascade if the attenuator's physicaltemperature is 290 K ?a)9 dBb)10.4 dBc)11.3 dBd)13.3 dBCorrect answer is option 'D'. Can you explain this answer?.
An amplifier has an operating spot noise figure of 10 dB when driven by a source of effective noise temperature 225 K.Que: If a matched attenuator with a loss of 3.2 dB isplaced between the source and the amplifier's input,what is the operating spot noise figure of the attenuator's amplifier cascade if the attenuator's physicaltemperature is 290 K ?a)9 dBb)10.4 dBc)11.3 dBd)13.3 dBCorrect answer is option 'D'. Can you explain this answer? for Electronics and Communication Engineering (ECE) 2024 is part of Electronics and Communication Engineering (ECE) preparation. The Question and answers have been prepared according to the Electronics and Communication Engineering (ECE) exam syllabus. Information about An amplifier has an operating spot noise figure of 10 dB when driven by a source of effective noise temperature 225 K.Que: If a matched attenuator with a loss of 3.2 dB isplaced between the source and the amplifier's input,what is the operating spot noise figure of the attenuator's amplifier cascade if the attenuator's physicaltemperature is 290 K ?a)9 dBb)10.4 dBc)11.3 dBd)13.3 dBCorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for Electronics and Communication Engineering (ECE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for An amplifier has an operating spot noise figure of 10 dB when driven by a source of effective noise temperature 225 K.Que: If a matched attenuator with a loss of 3.2 dB isplaced between the source and the amplifier's input,what is the operating spot noise figure of the attenuator's amplifier cascade if the attenuator's physicaltemperature is 290 K ?a)9 dBb)10.4 dBc)11.3 dBd)13.3 dBCorrect answer is option 'D'. Can you explain this answer?.
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